This invention relates to a beam splitter supplied with a single incident light beam having first second, and other wavelength components for splitting the incident light beam into first and second outgoing light beams having the first and the second wavelength components, respectively, and for splitting each of the first and the second outgoing beams into a plurality of partial light beams which may be called splitted light beams.
In Japanese Patent Publication No. 40,321/1978, a beam splitter is disclosed by Hashimoto et al. The Hashimoto et al beam splitter comprises a transparent block having first and second planar surfaces substantially parallel to each other. The first planar surface has an incident area and a remaining area. The second planar surface has a first exit area and another remaining area. The incident area is for receiving the incident light beam to direct the incident beam towards the first exit area.
A first band-pass layer has a band-pass filter characteristic and is formed on the first exit area. Supplied with the incident light beam, the first band-pass layer passes the first outgoing light beam and reflects the incident light beam except the first outgoing light beam towards the remaining area of the first planar surface. The remaining area of the first planar surface serves as a second exit area.
A second band-pass layer has another band-pass filter characteristic and is formed on the second exit area. Supplied with the incident light beam except the first outgoing light beam, the second band-pass layer passes the second outgoing light beam and reflects the incident light beam except the first and the second outgoing light beams towards the remaining area of the second planar surface. A different band-pass layer may be formed on the remaining area of the second planar surface for obtaining a different outgoing light beam having a different wavelength component.
However, Hashimoto et al never disclose that each of the first and the second outgoing light beams is furthermore splitted into a plurality of the partial or splitted light beams, each of which has the same wavelength component as the outgoing light beam in question has.
In U.S. Pat. No. 4,125,864 issued to John E. Aughton, another beam splitter is disclosed which splits a single incident light beam into a plurality of partial light beams, each of which has the same wavelength component as the incident light beam has. Merely for brevity of description, it will be assumed that the number of the partial light beams is two and that the partial light beams are called first and second partial light beams. The Aughton beam splitter comprises another transparent block having incident and outgoing planar surfaces substantially parallel to each other. The incident planar surface has an incident area and a reflection area on which a reflection layer is formed. The outgoing planar surface has first and second exit areas on which first and second semitransparent layers are formed, respectively.
The incident area receives the incident light beam and directs the incident beam towards the first semitransparent layer. Supplied with the incident light beam, the first semitransparent layer partially passes the incident light beams as the first partial light beam and partially reflects the incident light beam towards the reflection layer to make the reflection layer reflect the incident light beam towards the second semitransparent layer. Supplied with the incident light beam, the second semitransparent layer partially passes the incident light beam as the second partial light beam and partially reflects the incident light beam towards the reflection layer. Thus, the Aughton beam splitter splits the incident light beam into a plurality of the partial light beams which have the same wavelength component as the incident light beam has.
However, Aughton never teaches that the incident light beam has a plurality of wavelength components, such as first and second wavelength components, and that the incident light beam is splitted into a plurality of outgoing light beams which have the wavelength components, namely, the first and the second wavelength components, respectively.
An improved beam splitter is required which can produce a plurality of splitted light beams for each of wavelength components of an incident light beam and which can convert the incident light beam into the splitted light beams without a large optical energy loss.